The present invention relates to a magnetic pole material for use in magnetic disks, VTRs or the like, and, more particularly, to a heat resistant, high saturation magnetic flux density film having high saturation magnetic flux density, high permeability, and excellent heat and corrosion resistance, and to a magnetic head using the same.
Recently, magnetic recording technology has been highly developed, and the recording density has been raised significantly. In order to raise the recording density, it is necessary to use a recording medium having high coercive force. In order to magnetize a recording medium having high coercive force, a magnetic pole material having high saturation magnetic flux density must be employed. Therefore, a Ni--Fe alloy (permalloy) film or a Co amorphous alloy film has been employed as the magnetic pole material instead of conventional ferrite etc. Furthermore, it is necessary for the magnetic pole material to have excellent permeability for the purpose of improving the recording/reproducing efficiency as well as having the above-described high saturation magnetic flux density. Furthermore, it is necessary for the magnetic pole material to have excellent heat resistance so as to be capable of withstanding a heating process effected for forming the magnetic head, for the purpose of maintaining the excellent permeability.
In Japanese Patent Laid-Open No. 62-210607 and "MR 88-55" published by Electronic Communication Information Society, on Mar. 22, 1989, materials prepared by simultaneously adding: one kind selected from the group consisting of Nb, Zr, Ti, Ta, Hf, Cr, W and Mo; and nitrogen to a metal selected from a group consisting of Fe, Co, Ni and Mn has been disclosed. The above-described material can be prepared by a sputtering method in which the sputtering of a metal target having a predetermined composition is effected in a mixture gas of argon and nitrogen. According to the above-described disclosure, a film having a saturation magnetic flux density of 1.5 T and coercive force of 1 Oe or less can be obtained by alternately laminating nitride layers and non-nitride layers while modulating the nitrogen density in the sputtering gas. The coercive force of the above-described film can be maintained to a low level in a temperature range up to 600.degree. C. Therefore, it has heat resistance of 600.degree. C.
The inventors of the present invention examined supplementarily the above-described disclosure by sputtering an Fe--Nb material in a mixed gas of argon and nitrogen. As disclosed above, it was confirmed that the above-described material had low coercive force of 1 Oe or less at 400.degree. to 600.degree. C. However, the inventors have found such a problem in the above-described experiment that a part of the body-centered cubic crystal structure of Fe is transformed into a face centered cubic crystal structure when the temperature exceeds 600.degree. C. with the result that the saturation magnetic flux density of the obtained film is lowered due to the transformation. Furthermore, in this examination, the nitrogen gas must be intermittently introduced during sputtering. However, the intermittent introduction of the nitrogen gas while maintaining constant sputtering gas pressure needed complicated gas control.